Amyloid-beta Peptides in interaction with raft-mime model membranes: a neutron reflectivity insight
Year: 2016
Journal: Sci Rep
Authors: Rondelli, V; Brocca, P; Motta, S; Messa, M; Colombo, L; Salmona, M; Fragneto, G; Cantu, L; Del Favero, E
The role of first-stage beta-amyloid aggregation in the development of the Alzheimer disease, is widely accepted but still unclear. Intimate interaction with the cell membrane is invoked. We designed Neutron Reflectometry experiments to reveal the existence and extent of the interaction between beta-amyloid (A beta) peptides and a lone customized biomimetic membrane, and their dependence on the aggregation state of the peptide. The membrane, asymmetrically containing phospholipids, GM1 and cholesterol in biosimilar proportion, is a model for a raft, a putative site for amyloid-cell membrane interaction. We found that the structured-oligomer of A beta(1-42), its most acknowledged membrane-active state, is embedded as such into the external leaflet of the membrane. Conversely, the A beta(1-42) unstructured early-oligomers deeply penetrate the membrane, likely mimicking the interaction at neuronal cell surfaces, when the A beta(1-42) is cleaved from APP protein and the membrane constitutes a template for its further structural evolution. Moreover, the smaller A beta(1-6) fragment, the N-terminal portion of A beta, was also used. A beta N-terminal is usually considered as involved in oligomer stabilization but not in the peptide-membrane interaction. Instead, it was seen to remove lipids from the bilayer, thus suggesting its role, once in the whole peptide, in membrane leakage, favouring peptide recruitment.
